The present invention relates generally to systems and methods for directing a surgical instrument into a position relative to a tissue area whose position has been preselected. More specifically, the present invention relates to systems and methods adapted for directing a surgical instrument into a position relative to a lesion in the breast.
Techniques and devices available in the prior art for directing surgical instruments towards areas of breast tissue fall into two categories: those applicable to palpable lesions and those applicable to non-palpable lesions. Commonly, the use of these systems and methods result in a section of tissue being removed so that its gross and microscopic anatomy can be examined.
Palpable lesions are accessible by techniques commonly available in the medical arts, including the use of percutaneous techniques and the use of open surgical techniques. Percutaneous techniques involve the use of a medical device to reach a tissue area located beneath the skin surface without incising the tissues to approach the tissue area directly. Percutaneous techniques in surgery can include the formation of a skin incision through the epidermis and the dermis for the purpose of facilitating the introduction of the medical device through the skin, though the remainder of the delivery of the device to the tissue area takes place without further incisional exposure. Percutaneous techniques as applied to the breast include core needle biopsy and fine needle aspiration biopsy. Open surgical techniques are understood to involve the use of surgical methods to approach the tissue area directly. Surgical methods include incising the skin, and further include carrying the approach beneath the skin level to the area of tissue to be removed. Surgical methods include dissection, either sharp or dull, through an area of tissue. When a tissue area is palpable, the operator identifies the pertinent tissue area by palpation and uses this identification to guide the medical instrument to the desired area relative to the palpable tissue area.
When a tissue area is not palpable, other methods must be employed to identify its location and guide the medical instrument thereto. In the breast, non-palpable tissue areas can be identified through mammography and ultrasound. Other modalities available in the medical arts for the identification of tissue areas include CT scan and MRI, each with applicabilities well known in the medical arts. With reference to the breast, mammography is commonly employed to diagnose tissue areas that may contain possible foci of pathological changes that are cancerous or precancerous. Mammography permits the recognition of pathological tissue areas before they develop into palpable masses that may indicate more advanced cancers. When an abnormal area is identified by mammography, further diagnosis may be required. Such diagnosis may include a biopsy.
Systems and methods for biopsy of abnormalities identified on mammography are well known in the medical arts. A biopsy may be performed percutaneously or through an open surgical procedure. Either type of biopsy typically includes a way to localize the tissue area to be targeted with the biopsy device. As used herein, a tissue area of concern for a biopsy is termed a lesion. A palpable lesion can be localized by palpation. A non-palpable lesion that has been identified by mammography may be approached percutaneously for biopsy using mammography methods for guidance. If a percutaneous technique is used, the breast can be held in an apparatus that compresses it and that permits its radiological examination as a biopsy needle is directed towards the lesion. Mathematical methods to determine the location of the tissue area within the compressed breast allow more precision in directing the needle to the tissue area.
However, certain technical difficulties are understood to accompany the use of mammography systems to approach tissue areas for biopsy. For example, compression introduces certain artifacts and makes the position of the tissue area more difficult to locate precisely; this is a particular problem for lateral portions of tissue. Furthermore, multiple mammograms and multiple biopsies may need to be performed to give assurance that representative tissue sections have been obtained to diagnose the condition on the tissue area initially perceived on the screening mammogram. Although mechanized systems have been devised to automate the biopsy-taking process by taking multiple specimens or by taking a large specimen volume, the need for multiple mammograms and multiple biopsies often remains.
Surgical biopsies of non-palpable lesions must be also guided so that they reach the tissue area of concern. Commonly this takes place by a preliminary procedure such as a needle localization in which a needle tip is placed by the radiologist in the tissue area that has been identified mammographically. Typically, when a biopsy is guided by needle localization, the patient is taken to the mammography suite before the surgical biopsy for the placement of a guiding needle. As a first step, the patient is placed in a mammography machine, with her breast in mammographic compression. An upper compression plate containing an opening with a superimposed localizing grid is centered over the breast lesion. A mammography is performed in two perpendicular directions with the suspicious lesion placed in the opening of the grid. A radiologist then uses the grid seen on the mammograms to guide the placement of the prelocalization needle. A prelocalization needle is directed to the tissue area. The position of the needle is verified relative to the area requiring biopsy. Multiple needle positionings and mammographic confirmations may be required. When the appropriate position has been attained, a small wire with a hook at its end, called a wire, is placed through the bore of the needle so that its tip rests in the area requiring a biopsy. The needle is removed and the wire remains in place. The wire is secured so it will not become dislodged. The patient is transferred to the surgical suite, where she is prepared for the surgical biopsy. The surgeon uses the wire as a guide towards the area requiring biopsy. When the surgical biopsy is performed, a tissue sample is taken, corresponding with the amount of suspicious tissue seen on mammogram surrounding the needle tip. This excised tissue sample is mammogrammed after excision, and the film obtained from the specimen is compared with the original mammogram to confirm that the tissue area identified on the original mammogram has been adequately excised.
A surgical biopsy can be performed to remove a segment of tissue from a larger tissue mass that is abnormal-looking on mammography. The segment of tissue can then yield a diagnosis that then guides further therapy. Alternatively, if an abnormal-looking area has already been diagnosed, a surgical procedure can be performed that excises the entire abnormal area for definitive therapy. This procedure is termed a wide excision, because the abnormal area is excised widely, that is with a rim of normal tissue around it. As understood herein, the term biopsy can be applied to a wide surgical excision. Wide surgical excisions are currently commonly performed using needle localization techniques as described above, so the surgeon can identify the area within the breast to be excised. The term wide surgical excision, as used herein, includes what is commonly termed a lumpectomy.
Needle localization techniques have limitations. First, multiple positioning attempts and mammographic confirmations may be required. Second, when used as a preliminary procedure, the patient must usually be transported from the mammography suite to the operating suite, potentially increasing patient stress, time delay and procedure cost. Further, the surgical procedure cannot be carried out until the localization is complete, so if there is difficulty placing the localization wire, the surgical team and operating room remain in a state of readiness, wasting time and personnel resources. Third, there are inaccuracies that affect the accuracy of the J-wire in guiding the surgeon. For example, the wire may become dislodged, or its tip may not accurately reflect the best tissue area to be removed. Or, for example, there may be a shift of the J-wire with respect to the tissue area as the breast moves from the compressed to the non-compressed state. As another example, following the J-wire into the lesion may be technically difficult. As a further example, combining the J-wire position with the two-dimensional mammography images may not tell the surgeon enough about the three-dimensional shape of the lesion so that the surgeon can remove the lesion completely along with a rim of normal tissue around it. Because of the variety of inaccuracies that afflict needle localization guided biopsies, multiple surgical biopsies may be required to sufficiently remove the tissue area of concern. Multiple surgical biopsies may require additional surgical procedures, adding further to the patient""s suffering and anxiety, and multiplying medical costs.
It is desirable therefore to provide systems and methods that will yield accurate diagnosis of breast lesions without incurring the risks of imprecise needle localization. It is further desirable that a technique for biopsy be provided that is efficient, cost-effective and minimally stressful to the patient. It is also desirable that systems and methods be provided that facilitate the physician""s access to the lesion, for purposes of biopsy or extirpation.
In one embodiment, the present invention includes systems for placing a surgical instrument into a spatial relationship with a lesion. The system may include a data translation system that translates a set of data points that identify the lesion in at least two two-dimensional planes into a set of three-dimensional coordinates that identify the position of the lesion in three-dimensional space. The system may also include a tracking system that is related to the surgical instrument that generates tracking signals for identifying the position of the surgical instrument in three-dimensional space. The system may also include a representation system that produces a representation of the positions of the surgical instrument and the lesion in three-dimensional space relative to each other, based on the signals generated by the tracking system and the set of three-dimensional coordinates produced by the data translation system, wherein the placement of the surgical instrument into spatial relationship with the lesion is guided by reference to the aforesaid representation.
In one embodiment, the present invention includes a system for guiding the placement of a surgical instrument into spatial relationship with a lesion including a data translation system, a positioning system, a tracking system and a representation system. In this embodiment, the data translation system may translate a set of data points identifying the lesion in at least two two-dimensional planes into a set of three-dimensional coordinates that identify the lesion in three-dimensional space. In this embodiment, the positioning system may identify the position of the lesion in three-dimensional space relative to a three-dimensional position of at least one anatomic landmark. In this embodiment, the tracking system may be disposed in relation to the surgical instrument to generate tracking signals identifying the position of the surgical instrument in three dimensional space. In this embodiment, the representation system may produce at least one representation of the position of the surgical instrument in three-dimensional space related to the position of the lesion or the spatial landmark, so that the placement of the surgical instrument into spatial relationship with the lesion is guided by reference to the representation.
In one embodiment, the invention includes a mammography system for orienting a breast to facilitate the biopsy of a breast lesion. In this embodiment, the mammography system includes a mammography device that may obtain mammograms in at least two different planes and that may obtain mammograms in a plurality of planes relative to a defined axis of the breast, a first set of mammograms that identify the position of the lesion within the breast, a first set of two-dimensional coordinates corresponding to the first set of mammograms, an adjustment system that generates a set of positional instructions that direct the positioning of the mammography device relative to the breast for obtaining a second set of mammograms that show the lesion centrally located on at least one film, and a compression system for securing the breast so that the position of the lesion within the breast corresponds to the position of the lesion located on the second set of mammograms.
In another embodiment, the invention includes a method for obtaining a tissue sample from the breast. This practice of the invention includes identifying the position of the target tissue on at least two mammograms, digitizing data correlated with the mammograms, determining the position of the target tissue in three dimensional space using the digitized data, providing a surgical instrument suitable for obtaining a sample of the target tissue, electronically tracking the position of the surgical instrument relative to the target tissue, creating a two-dimensional representation of the position of the surgical instrument, directing the surgical instrument to the target tissue by referring to the two-dimensional representation, and using the instrument to obtain a sample of the target tissue.